THE DISTRIBUTION AND AGE OF ASYMPTOTIC GIANT BRANCH STARS IN NGC-205

被引:19
作者
DAVIDGE, TJ [1 ]
机构
[1] CANADA FRANCE HAWAII TELESCOPE CORP,KAMUELA,HI 96743
关键词
GALAXIES; ELLIPTIC AND LENTICULAR; CD; EVOLUTION; INDIVIDUAL; (NGC-205); STELLAR CONTENT;
D O I
10.1086/171802
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
V and I CCD images are used to investigate the spatial distribution and age of bright asymptotic giant branch (AGB) stars in the central regions of the Local Group dwarf elliptical galaxy NGC 205. These data reveal a large intermediate-age component, which is uniformly distributed over the central regions of the galaxy. The redward extent of the bright AGB sequence on the (I, V-I) diagram suggests that the majority of these objects have metallicities which are roughly solar. The most luminous AGB stars occur near M(bol) approximately -5.5, while the density of AGB stars within 1' of the galaxy center, measured as a function of surface brightness is constant. Moreover the bolometric luminosity function of AGB stars does not show spatial variations and is different from that seen in dwarf irregular galaxies, where stars with M(bol) < -6 are detected. The data suggest that star formation has not been continuous in NGC 205, and it appears that the size of the most recent burst of star formation, of which the central concentration of early-type stars is the most conspicuous signature, was relatively minor compared with what occurred 0.5-1 Gyr in the past. It is speculated that the appearance of NGC 205 during intermediate epochs may have been similar to the gas-rich dwarf galaxy NGC 3077, a member of the M81 group which is currently experiencing a large burst of star formation.
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页码:457 / 462
页数:6
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